The army and the Shi‘ite forces advanced east and south of the Sunni-rebel held bastion of Beit Jin backed by some of the heaviest aerial bombing and heavy artillery shelling since a major assault began over two months ago to seize the area, rebels said.

The Syrian army said it had encircled the village of Mughr al Meer at the foothills of Mount Hermon as troops moved toward Beit Jin amid fierce clashes. The enclave is the last rebel bastion left in the south west of Damascus known as the Western Ghouta that had since last year fallen under government control after months of heavy bombing on civilian areas and years of siege tactics that forced rebels to surrender.

“The Iranian backed militias are trying to consolidate their sphere of influence all the way from southwest of Damascus to the Israeli border,” said Suhaib al Ruhail, an official from the Liwa al Furqan rebel group that operates in the area.

Iran has never hid the fact that it is a strong supporter of Syrian President Bashar Al-Assad and has been providing him with both financial aid and military advisors against a range of opposing forces. Near the start of the Syrian civil war, it was reported that then-Iranian President Mahmoud Ahmadinejad had personally sanctioned the dispatch of officers from the Iranian Revolutionary Guards to Syria to fight alongside Assad’s troops.

Worried by Iran’s expanding influence in Syria after the defeat of Islamic State, Israel has in the last few weeks stepped up its strikes against suspected Iranian targets inside Syria. Early this month an Israeli strike on a base near Kiswah, south of Damascus was widely believed to be an Iranian military compound, according to a Western intelligence source.

As previously reported earlier this month, the commander of one of the Iranians’ most important militias was recorded taking a tour along the Israel-Lebanon border accompanied by Hezbollah terrorists. The commander, Qais al-Khazali, is wanted by the U.S. and even served time in a U.S. prison. He is considered one of the prominent leaders of the Iraqi battle against ISIS.

“We announce that we’re fully prepared to stand with the Lebanese people and with the Palestinians against the tyrannical Israeli occupation that is hostile to Islam, Arabs, and humanity,” said al-Khazali during his tour near the border.

The southwest of Syria is part of a de-escalation zone in southern Syria agreed last July between Russia and Washington, the first such understanding between the two powers. The area has not seen Russian bombing unlike other ceasefire areas in Syria.

Diplomatic sources say several thousand Shi‘ite fighters who have been amassing from outside the Quneitra province are pitted against hundreds of Islamist and mainstream Free Syria Army (FSA) rebels closing ranks under the banner of Itihad Quwt Jabal al-Sheikh “Union of fighters of Jabal al-Sheikh”. They are mainly drawn from local fighters from the area.

“The Iranian backed militias are trying to consolidate their sphere of influence all the way from southwest of Damascus to the Israeli border,” Suhaib al Ruhail, an official from the Liwa al Furqan rebel group, was quoted in the report.

With the army and Iranian backed offensive widening, the rebels have called on youths to enlist as mosque imams in Beit Jin called on people to take up arms and fight the army. Rebels still have a sizeable presence in central and southern Quneitra, in the Syrian Golan Heights.

Western diplomatic sources say the crushing of the Sunni rebel presence in areas they have been in since 2013 will allow Lebanon’s Hezbollah to open another secure arms supply line from its border in southern Lebanon into Syria.

Since the beginning of the conflict in Syria, Iran has had a growing presence in the country, deploying thousands of Shi‘ite fighters who have fought against both mainstream Sunni rebel groups and more militant groups.